The present invention relates to a sensor for sensing wheel speed in a vehicle powered by a hydrostatic motor. In particular, the present invention relates to a mounting that is adapted for utilizing the existing hydrostatic motor carrier and output drive shaft for mounting a sensor in a location where it is not susceptible to damage.
In compact loaders, such as all-wheel drive, all-wheel steer loaders, it is desirable to accurately sense the speed of the wheels on each side of the vehicle to efficiently control operation and insure that the wheel speeds are properly controlled. The signals representing wheel speed can be coordinated with a sensed angle of steer and used in a control algorithm to reduce the speed of the inside wheels on a turn in order to prevent skidding during the turn.
In compact industrial vehicles, space is at a premium and mounting sensors that will provide an accurate indication of wheel speed is difficult because of the need to protect the sensors from damage during use, and be out of the way as well as conserving space.
The present invention relates to a sensor for sensing the rotation of a positive drive shaft driving the wheels of a vehicle, such as a compact four-wheel loader. The sensor is mounted with a unique bracket onto a motor carrier or support and it is used in connection with a rotating disc having rotational position identifiers that provide a pulse as they pass a stationary sensor as the disc rotates. The disc is attached to the output shaft of the motor. The output shaft is used for driving sprockets that in turn drive chains to the final drive axles of the vehicle.
The bracket is a simple T-shaped bracket that is supported on the motor carrier, or other portions of the motor frame. The bracket carries a Hall effect sensor that has a sensing end projecting from the carrier. The disc position identifiers are disclosed as alternating pole magnets, that is, a south pole magnet facing the sensor is followed by next adjacent magnet having a north pole facing the sensors. As these magnets pass next to the Hall effect sensor, the well known effect of a pulse is obtained to indicate rotation of the shaft. The rate of the pulses indicates the wheel speed.
The sensor is connected to a suitable computer where the signal for wheel speed is used in a desired manner, again, for example, for coordinating the wheel speed and angle of steer of wheels being driven, so that a differential action can be obtained during turns, and positive control of the forward or rearward velocity of the vehicle can be obtained as well.